An object detecting apparatus in which an FM/CW wave whose frequency is made to rise and fall in a triangular waveform with time is transmitted, a wave reflected from an object is received, a beat signal obtained by mixing the transmitted signal and the received signal is subjected to frequency analysis, and frequencies on the rising side and the falling side of the reflected peak thus obtained are used to give the distance to the object and the relative speed is known from Patent Document 1 below.
In order to calculate the distance and relative speed of an object by an FM/CW type radar device, it is necessary to combine, of waves reflected from the same object, a reflected peak of an up beat signal and a reflected peak of a down beat signal that correspond to each other (this is called pairing).
However, in the FM/CW type radar device, for example, a fan-shaped detection region having an angle of 16° to the left and to the right is scanned by, for example, 16 beams having a detection area with 1° to the left and to the right, and when an object such as a vehicle is a detection target, a plurality of beams impinge on the object. As a result, reflected waves from one object include a plurality of pairs of up beat signal reflected peak and down beat signal reflected peak, and unless pairing thereof is carried out appropriately, the distance and relative speed of the object cannot be calculated with good precision.
Conventionally, as a pairing method for calculating distance and relative speed of an object using an FM/CW type radar device, a 1 beam pairing method or a field pairing method is employed.
The 1 beam pairing method is one in which pairing is carried out using 1 beam unit having a detection area of 1° to the left and to the right, those having distances and relative speeds that are close are collected together, and the distance and relative speed of one object are calculated.
The field pairing method is one in which those contained in a detection region of 16° to the left and to the right that have up beat signal reflected peak frequency and left-and-right direction angle that are close are collected together, those having down beat signal reflected peak frequency and left-and-right direction angle that are close are collected together, and the frequencies of the reflected peaks of these two collected groups are paired, thus calculating the distance and relative speed of one object.    Patent Document 1: Japanese Patent No. 3305624